Components, for example turbine blades, turbine vanes, combustion chamber walls, combustion chamber tiles, of gas turbine engines and other turbomachines are cooled to maintain the component at a temperature where the material properties of the component are not adversely affected and the working life and the integrity of the component is maintained.
One method of cooling components, turbine blades, turbine vanes, combustion chamber walls, combustion chamber tiles, of gas turbine engines provides a film of coolant on an outer surface of a wall of the component. The film of coolant is provided on the outer surface of the wall of the component by a plurality of effusion cooling apertures which are either arranged perpendicular to the outer surface of the wall or at an angle to the outer surface of the wall. The effusion apertures are generally manufactured by laser drilling, but other processes may be used, e.g. electro-chemical machining or electro-discharge machining. Effusion cooling apertures are often cylindrical and angled in the direction of flow of hot fluid over the outer surface of the component. Angled effusion cooling apertures have an increased internal surface area, compared to effusion cooling apertures arranged perpendicular to the outer surface of the wall of the component, and the increased internal surface area increases the heat transfer from the wall of the component to the coolant. Angled effusion apertures provide a film of coolant on the outer surface of the component which has improved quality compared to effusion cooling apertures arranged perpendicular to the outer surface of the wall of the component.
In addition a thermal barrier coating is applied onto the outer surface of the wall of the component to further reduce the temperature of the component due to convective and radiant heat transfer, to improve the thermal shock capability of the material of the component and to protect the component against corrosion and oxidation.
A number of problems arise when providing a thermal barrier coating onto the outer surface of a component which is to be cooled.
One method of manufacturing a cooled component with a thermal barrier coating is to deposit the thermal barrier coating onto the outer surface of the component and then drill the effusion cooling apertures through the thermal barrier coating and the wall of the component. However, this may result in the loss of the thermal barrier coating immediately adjacent to the effusion cooling apertures and this may lead to early failure of the component due to hot spots, oxidation and/or corrosion.
Another method of manufacturing a cooled component with a thermal barrier coating is to drill the effusion cooling apertures through the wall of the component and then to deposit the thermal barrier coating onto the outer surface of the wall of the component. However, this may result in blockage or partial blockage of one or more of the effusion cooling apertures and this may result in early failure of the component due to hot spots. It is known to use various methods to prevent blockage of the effusion cooling apertures by providing temporary fillers in the effusion cooling apertures during the deposition of the thermal barrier coating, but this necessitates the additional expense of removing all of the temporary fillers and inspecting to make sure all of the temporary fillers have been removed. It is also known to remove the blockage from the effusion cooling apertures after the thermal barrier coating has been deposited using high pressure water jets or abrasives etc, but this also necessitates the use of water jets and/or abrasive to remove the thermal barrier material blocking the effusion cooling apertures and inspecting to make sure all of the thermal barrier material blocking the apertures has been removed.
Therefore the present disclosure seeks to provide a novel cooled component which reduces or overcomes the above mentioned problem.